netdev - RE: [PATCH v3 3/6] bpf: add BPF_PROG_ATTACH and BPF_PROG

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Date:   Mon, 5 Sep 2016 15:30:08 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Daniel Mack' <daniel@...que.org>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
CC:     "htejun@...com" <htejun@...com>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "ast@...com" <ast@...com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kafai@...com" <kafai@...com>, "fw@...len.de" <fw@...len.de>,
        "pablo@...filter.org" <pablo@...filter.org>,
        "harald@...hat.com" <harald@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "sargun@...gun.me" <sargun@...gun.me>
Subject: RE: [PATCH v3 3/6] bpf: add BPF_PROG_ATTACH and BPF_PROG_DETACH
 commands

From: Daniel Mack
> >> +
> >> +	struct { /* anonymous struct used by BPF_PROG_ATTACH/DETACH commands */
> >> +		__u32		target_fd;	/* container object to attach to */
> >> +		__u32		attach_bpf_fd;	/* eBPF program to attach */
> >> +		__u32		attach_type;	/* BPF_ATTACH_TYPE_* */
> >> +		__u64		attach_flags;
> >> +	};
> >
> > there is a 4 byte hole in this struct. Can we pack it differently?
> 
> Okay - I swapped "type" and "flags" to repair this.

That just moves the pad to the end of the structure.
Still likely to cause a problem for 32bit apps on a 64bit kernel.
If you can't think of any flags, why 64 of them?

	David